Thread: Importing Third Party Libraries

Am trying to complete the Java tutorial on Block Chain at "https://medium.com/programmers-blockchain/create-simple-blockchain-java-tutorial-from-scratch-6eeed3cb03fa" and am having problems getting the import to work in MyEclipse. Regardless of whether I follow the method shown in the tutorial or imprt it the way I used to do I get aan error on the import line in the file NoobChain.java. Where am I going wrong?

Found 3 different ways to put a jar file in the class path.
First , there is the method from the tutorial which places the jar file in a directory with an arbitrary name which is on the same level as the JRE System Library
Second, do not create a User Library just add the jar to the build path which installs it in a directory call Referenced Libraries
Third, create a directory at project root called lib and place the jar in it and open it (did not open)
All of these methods failed to eliminate the the import error
Have used the last two before with no problems

Originally Posted by Norm

Is the spelling of the path used on the import statement correct? Java is case sensitive.
Try using the commandline statement I gave earlier to see if the javac command finds the class when given the path to the jar file on the command line.
Please copy the full text of the error message and paste it here. It has important info about the error.
Moving to IDE section.

I did try the commandline you suggested, tried it in a cmd window and a terminal out of MyEclipse. In both I was told that 'javac' is not recognized as an internal or external command,
operable program or batch file. So I check the system variables and found that contrary to the before Oracle JDK instilation does not include setting path and JAVA_HOME. I set them and restarted the cmd window and the MyEclipse terminal. The system indicates the path and JAVA_HOME values were correct but javac could not be found. The terminal showed no change in the variables and javac could not be found.
In the tutorial step before adding gson to the project it compiled and ran with the expected results, not sure how it could do that.

Originally Posted by Norm

To help the OS find a command, add the path to the folder containing the command to the PATH environment variable.
How does it do that? The proof of correctness is when the OS finds the command on the path.
You can also give the full path to the command in the command prompt window:
C:\Program Files\Java\jdk1.8.0_60\bin\javac.exe -cp . -Xlint -Xdiags:verbose TestCode25.java
Also:
Please copy the full text of the error message and paste it here. It has important info about the error.

I don't remember having to put all of the files in jdk bin directory in the path in order to use them. Expect JAVA_HOME to help with that. (https://www.cs.unm.edu/~ralovato/cs2...h-windows.html)

I does it because I when I open a comand console and type "echo %path%" it prints out
"C:\Users\JAJones>echo %path%"
"C:\Program Files\Java\jdk1.8.0_201\bin;C:\Program Files (x86)\Razer Chroma SDK\bin;C:\Program Files\Razer Chroma SDK\bin;C:\Windows\system32;C:\Windows;C:\Windows\ System32\Wbem;C:\Windows\System32\WindowsPowerShel l\v1.0\;C:\Windows\System32\OpenSSH\;C:\Windows\sy stem32\config\systemprofile\AppData\Local\Microsof t\WindowsApps;C:\Users\JAJones\AppData\Local\Micro soft\WindowsApps;"
When I open an Eclipse console and type "echo %path%" I get:
C:\Users\JAJones>echo %path%
C:\Program Files (x86)\Common Files\Oracle\Java\javapath;C:\Program Files (x86)\NVIDIA Corporation\PhysX\Common;C:\Program Files (x86)\Razer Chroma SDK\bin;C:\Program Files\Razer Chroma SDK\bin;C:\Windows\system32;C:\Windows;C:\Windows\ System32\Wbem;C:\Windows\System32\WindowsPowerShel l\v1.0\;C:\Windows\System32\OpenSSH\;C:\Windows\sy stem32\config\systemprofile\AppData\Local\Microsof t\WindowsApps;C:\Users\JAJones\AppData\Local\Micro soft\WindowsApps;
BTW JAVA_HOME is set to "C:\Program Files\Java\jdk 1.8.0_201\bin"

When I enter: "C:\Program Files\Java\jdk1.8.0_201\bin\javac.exe -cp . -Xlint -Xdiags:verbose NoobChain.java" from "C:\Users\JAJones\Workspaces\BlockChain\noobch ain" (project root) I get "The filename, directory name, or volume label syntax is incorrect". (command console)
Tried issuing the command in the src directory and using "src\NoobChain.java"

Seems my system is hopelessly messed up

C:\Users\JAJones\Workspaces\BlockChain\noobchain\s rc\noobchain>javac NoobChain.java
NoobChain.java:4: error: package com.google.gson does not exist
import com.google.gson.GsonBuilder;
^
NoobChain.java:8: error: cannot find symbol
public static ArrayList<Block> blockchain = new ArrayList<Block>();
^
symbol: class Block
location: class NoobChain
NoobChain.java:8: error: cannot find symbol
public static ArrayList<Block> blockchain = new ArrayList<Block>();
^
symbol: class Block
location: class NoobChain
NoobChain.java:12: error: cannot find symbol
blockchain.add(new Block("Hi im the first block", "0"));
^
symbol: class Block
location: class NoobChain
NoobChain.java:13: error: cannot find symbol
blockchain.add(new Block("Yo im the second block",blockchain.get(blockchain.size()-1).hash));
^
symbol: class Block
location: class NoobChain
NoobChain.java:14: error: cannot find symbol
blockchain.add(new Block("Hey im the third block",blockchain.get(blockchain.size()-1).hash));
^
symbol: class Block
location: class NoobChain
NoobChain.java:16: error: cannot find symbol
String blockchainJson = new GsonBuilder().setPrettyPrinting().create().toJson( blockchain);

^
symbol: class GsonBuilder
location: class NoobChain
7 errors

javac NoobChain.java

C:\Users\JAJones\Workspaces\BlockChain\noobchain\s rc>javac noobchain\NoobChain.java
noobchain\NoobChain.java:4: error: package com.google.gson does not exist
import com.google.gson.GsonBuilder;
^
noobchain\NoobChain.java:16: error: cannot find symbol
String blockchainJson = new GsonBuilder().setPrettyPrinting().create().toJson( blockchain);

^
symbol: class GsonBuilder
location: class NoobChain
2 errors

The jar file is in the Referenced Libraries directory which shows up in MyEclipse but not in the cmd console, Why?

C:\Users\JAJones\Workspaces\BlockChain\noobchain\s rc>javac -cp .;C:\Users\JAJones\Downloads\Java_Libraries\gson-2.6.2.jar noobchain\NoobChain.java
it compiled

--- Update ---

Originally Posted by Norm

Is that inside of the Eclipse program? I don't use Eclipse and don't know how to configure it.
That was the reason I suggested the use of the javac command with the -cp option in a command prompt window completely outside of Eclipse.

If the command:
javac -cp .;<Path to jar file> NoobChain.java
worked, then you would know that the source code and jar file were correctly connected.

Can you try that command in a command prompt window open in the folder with the source file and then copy the full contents of the command prompt window and paste it here?

cmd console is wwhat used to be called the dos prompt run cmd

yes it is the package

For the sake of later readers this is what I got from the MyEclipse support
Your project has module-info.java file which is introduced from Java 9 onwards.
Please read these for more details about modules :
https://www.oracle.com/corporate/fea...9-modules.html
Module Directives in Java 9 - codeNuclear

If there is a module-info.java file in the project, then you need to add the jar to the Modulepath section in the Libraries tab instead of Classpath and then declare the module dependencies in the file. For this case of gson jar, this is how the module-info.java file should look :

1
2
3
module noobchain {
requires gson;
}
Please make the changes accordingly and let us know how it works.

–Swapna
Genuitec Support[COLOR="Silver"]